Anti-corrosive properties of superhydrophobic coating on steel obtained by electrochemical method

The protective efficiency of a superhydrophobic (SHP) coating on a steel electrode obtained by electrodeposition of copper and zinc with subsequent treatment in an ethanol solution of myristic acid was studied in a number of environments. The SHP coating is characterized by a contact wetting angle equal to 157±2°. Corrosion tests were carried out gravimetrically under conditions of 100% humidity, distilled water, in the gas and liquid phases of 1 and 3% SO2 solutions, as well as NaCl (50 g/L) and NACE (g/L: NaCl – 5; СH3 COOH - 0,25) in the presence of 1 excess atmosphere of CO2 for 240 h. The superhydrophobic coating exhibits 100% protective effect Z when samples are exposed to 100% humidity and distilled water at a virtually constant value of contact angles. In the gas phase of NaCl + CO2 and NACE + CO2 solutions, the protective effect is 78 and 71% respectively. In the first case, superhydrophobicity is retained, in the second - hydrophobicity, but subsequent exposure to air helps restore superhydrophobicity. After the liquid phase, the coating retains its hydrophobicity, but its superhydrophobicity is not restored when exposed to air. In the gas phase of 1 and 3% SO2 solutions, Z is 94 and 64% respectively. In the first case, the coating retains its superhydrophobicity, while in the second case, it retains its hydrophobicity, which, however, turns into superhydrophobicity when exposed to air. Polarization and impedance measurements in a NaCl solution for 168 hours showed that the presence of the SHP coating on the steel electrode causes a slowdown in the anodic process on the electrode compared to an unprotected electrode. The Z value of the coating at the initial moment is close to 90% and decreases over time, reaching 70% after 168 hours.

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